1. Field of the Invention
The present invention relates to an image processing machine (such as a copying machine) that can process (e.g., copy on a copy sheet) an image on each side of an original sheet equipped with a document handler that can automatically reverse the original sheet.
2. Related Art
An example of a conventional automatic reversible sheet handler for use with a copying machine is explained according to the Japanese Published Unexamined Patent Application Nos. H1-117167 and H1-167125. The sheet handler includes: an initial tray on which a plurality of original sheets are stacked; a placing mechanism for taking the uppermost sheet of the initial tray and placing it on a contact glass through which the image of the sheet is copied; a sheet remover for removing the sheet from the contact glass; a reverser for reversing the sheet removed from the contact glass and placing it again onto the contact glass; and an ejecting mechanism for reversing the sheet removed from the contact glass and ejecting it to a final tray.
The movement of the sheets in the sheet handler is explained referring to FIGS. 5A, 5B, 6A and 6B. First a "simple mode" function of the sheet handler is explained. In FIG. 5B, four original sheets R1, R2, R3 and R4 are stacked on an initial tray 1, and the printed surface of each sheet is downside (the triangle indicates the printed surface, and the number in the triangle is the page number). When the sheet handler is activated in the simple mode, the uppermost sheet R4 is first taken in and placed on the contact glass. After the printed surface of the sheet R4 is copied, the sheet R4 is removed from the contact glass, reversed upside down, and laid on a final tray 3 (FIG. 5A). The next sheet R3 is similarly carried and laid upon the previous sheet R4 on the final tray 3. Thus, when all the sheets are copied, the sheets are stacked on the final tray 3 as shown in FIG. 5A. Note that the page order of the original sheets on the initial tray 1 is maintained on the final tray 3.
In a "reverse mode", a plurality of (two in the case of FIG. 6A and 6B) two-sided (i.e., each side of the sheet is printed) sheets R1 and R2 are stacked as shown in FIG. 6B on the initial tray 3. When the sheet handler is activated in the reverse mode, the uppermost sheet R2 is first taken out from the initial tray 1 and, not directly placing it on the contact glass, but reversed upside down before placing it on the contact glass. After the page 4 of the sheet R2 is first copied on the contact glass, the sheet R2 is reversed and the page 3 is copied. When the sheet R2 is removed from the contact glass after the both surfaces are copied, the sheet R2 is further reversed and laid on the final tray 3. As shown in FIG. 6A, page 4 of the sheet R2 faces down on the final tray 3. The next sheet R1 is similarly handled and laid onto the previous sheet R2 on the final tray 3 as shown in FIG. 6A. In this mode also the page order of the original sheets on the initial tray 1 is maintained on the final tray 3.
As explained above, when two-sided sheets are handled by the conventional sheet handler, every sheet is reversed three times in order to maintain the page order. Such sheet handler does not match a high speed copying machine.
An improvement addressing the problem is made in Japanese Patent Application No. H1-192544, in which the improved sheet handler includes: an initial tray on which a plurality of original sheets are stacked; a placing mechanism for taking the uppermost sheet on the initial tray and placing it on a contact glass through which the contact surface (downward surface) of the sheet is copied; a reverser for reversing the sheet removed from the contact glass and placing it again onto the contact glass; and an ejecting mechanism for removing the sheet from the contact glass and either a) ejecting the sheet onto a first final tray after reversing or b) ejecting the sheet onto a second final tray without reversing. The sheet handler can also operate in a simple mode or in a reverse mode. In the simple mode, an original sheet on the initial tray is placed on the contact glass and the contact surface of the sheet is copied. Then the sheet is reversed after it is removed from the contact glass, and ejected onto the first final tray. In the reverse mode, a sheet on the initial tray is placed on the contact glass and the contact surface of the sheet is copied. After the first surface is copied, the sheet is reversed upside down to make the second surface face the contact glass and the second surface is copied. After both surfaces are copied, the sheet is ejected onto the second final tray without reversing. In the reverse mode, the finished original sheets stacked on the second final tray maintain the original page order at the initial tray.
The sheet handler is improved in the treating time, but it has a drawback. The order of copying operation is irregular, i.e., the copying order will be as [page 3.fwdarw.page 4.fwdarw.page 1.fwdarw.page 2] if the two-sided original sheets are naturally prepared as shown in FIG. 6B on the initial tray 1.